The present invention relates to robotic systems and may find particular use in robotic lawnmowers, and charging and control systems suitable for robotic lawnmowers.
By their very nature, autonomous machines such as robots represent a significant labour-saving for consumers. Repetitive and time-consuming tasks may now be carried out without significant supervision or instruction by the user of such autonomous machines. In order to further reduce the amount of supervision and instruction necessary, sophisticated control systems have been proposed that further increase the independence of the machines. Additionally, where an autonomous machine is able to move, in order to increase its independence of the user it may be provided with a chargeable internal power-source and be programmed, or otherwise configured, to engage with a charging station in order to re-charge the internal power-source.
Robotic lawnmowers are a particularly commercially successful example of such an autonomous machine, substantially reducing the time and effort required on the user's part in order to maintain a neatly-kept lawn. Typically, robotic lawnmowers will be provided with an internal power-source and will return periodically to a charging station to recharge this power source, as described above. Such an internal power-source obviates the need for power cabling connected to the lawnmower during use, which could become tangled, or severed by the blade of the lawnmower.
The charging station for the lawnmower may be positioned within the working area or at its boundaries, so that when the robot battery is getting flat, the robot may automatically return to the charging station to charge the internal power-source for the next operation. The charging station is provided with a power supply, usually at low voltage (less than 48V to prevent electric shock), which may be linked by an electrical cable to an indoor outlet, or a protected outdoor mains outlet, or alternatively to a charger.
Robotic lawnmowers also include control systems, as described briefly above, in order to govern, amongst other things, the movement of the lawnmower and the operation of its blade. There is typically provided, as part of such a control system for currently-available robotic lawnmowers, a position locating network that enables the lawnmower to sense its current relative position, when it is operating away from the charging station.
A typical example in a commercially available system is a boundary wire that is utilised to demarcate a working area, within which the lawnmower is permitted to move. Such a boundary wire generally carries a low-frequency, low-voltage signal that may be detected by the robot so that the robot can locate its relative position to the wire and in particular, whether it is inside or outside of the boundary wire loop and its proximity to the wire. Typically, the signal is generated by a signal generator device that forms a further part of the charging and control system and is linked directly to the boundary wire, so as to limit losses that would be experienced over any linking wiring, and also to avoid the increase in cost that is associated with such linking wiring.
The signal generator, being an active component, also requires a power source and typically therefore shares the power source of the charging station. Since both the charging station and the signal generator are both commonly desired to be in close proximity to the boundary wire, they are therefore often located in close proximity to each other.
Accordingly, the signal generator is located outdoors and thus a well-sealed enclosure to the electronics is required, which ideally would be able to sustain the winter. Alternatively, the user is required to disconnect the signal generator and bring it indoors during the winter to prevent damage by the weather.
Since it may be desirable, for the reasons noted above, to locate the charging station and signal generator in close proximity it has further been proposed to provide both the charging station and the signal generator within the same weather-proofed housing, so that only one weather-proofed housing is required. However, such a system complicates maintenance for the end-user, since the whole housing may need to be returned, even if only the signal generator is defective.
Further, while it might generally be desirable that the charging station be placed relatively close to its power supply, it may be desirable given, for example, the particular topography or obstacles present, for the charging station to be placed a long distance from its power supply. An example of such a situation is where a garden is sloped away from the power supply: if the charging station is placed close to the power supply, the robot must travel uphill to recharge and may run out of charge in an attempt to do so before reaching the charging station; however, if the charging station is placed at the bottom of the slope a very long power cable may be required to stretch from the power supply to the charging station.
Often an end-user may wish to carry out several test-runs with the lawnmower to discover where the most effective place to situate the charging station is. In a case, such as that just described, where the most effective performance is felt when the charging station is far from its power supply, the end-user may need to buy a longer power cable than the one in their possession, or an extension cable, or the like. Thus, the end-user may be left with the undesirable prospect of having to invest yet more money into making a system that he has already purchased work optimally.